Aims: To evaluate the usefulness of a quantification method using filter paper for analyzing minute voided urine of the mouse.
Methods: Voided stain on paper (VSOP) method; the correlation between area of stained spot on a filter paper and amount of applied liquid was calculated. Voiding behavior of the mice was analyzed by placing the animal above the same filter paper and recording voided time and area over 2 hr. The usefulness of the VSOP method was tested in analysis of the voiding behavior of five female 7-week-old ddY mice treated with cyclophosphamide (CPM, 150 mg/kg, intraperitoneally) and five control ones, in comparison with the histology of CPM-induced cystitis. Further, the voided volume of male and female ddY mouse ranging from 2 to 13 weeks was assessed.
Results: There was a linear correlation between liquid volume and stained area on the filter paper (y = 16.472x - 22.411, R(2) = 0.9981). Between control mice and those with histologically proven CPM cystitis, there was a significant difference in voided volume (362.7 +/- 51.9 and 127.8 +/- 100.0 microl, < 0.001) and voiding interval (10.30 +/- 3.10 and 4.47 +/- 1.70 min, < 0.001). Voided volume of ddY mice was quantifiable from as early as 2-week old, increased along with their growth and correlated well with their body weight [(voided volume: microl) = 10.8 x (body weight: g) + 32, R(2) = 0.762].
Conclusions: The VSOP method is a useful tool for evaluating voiding behavior of the mouse, including those with small bladder capacity.